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Abstract:

A system that incorporates teachings of the subject disclosure may
include, for example, a method for analyzing a wide frequency band with
respect to signal power levels in specified narrow frequency bands,
detecting narrow band signal power levels received in the specified
narrow frequency bands, determining an average composite wideband power
level from the narrow band signal power levels, determining an adaptive
threshold from the average composite wideband power level, detecting
narrow band interference according to the adaptive threshold, and
configuring a filter to substantially suppress the detected narrow band
interference. Other embodiments are disclosed.

Claims:

1. A method, comprising: analyzing a wide frequency band with respect to
signal power levels in specified narrow frequency bands; detecting narrow
band signal power levels received in the specified narrow frequency
bands; determining an average composite wideband power level from the
narrow band signal power levels; determining an adaptive threshold from
the narrow band signal power levels; detecting narrow band interference
according to the adaptive threshold; and configuring a filter to
substantially suppress the detected narrow band interference.

2. The method of claim 1, wherein each of the specified narrow frequency
bands has a bandwidth that is substantially smaller than the wide
frequency band, and wherein the adaptive threshold has a power level that
exceeds the average composite wideband power level.

4. The method of claim 1, wherein the threshold is configured for
hysteresis.

5. The method of claim 1, wherein the threshold comprises more than one
threshold.

6. The method of claim 1, wherein the detecting of the narrow band
interference according to the adaptive threshold comprises detecting a
plurality of narrow band interferers having power levels that exceed the
adaptive threshold.

7. The method of claim 1, wherein the filter comprises a plurality of
sub-filters, and wherein the method comprises configuring each of the
plurality of sub-filters to substantially suppress the plurality of
narrow band interferers.

8. The method of claim 7, wherein the filter has a variable stop band.

9. The method of claim 1, wherein the analyzing of the wide frequency
band, the detecting of the narrow band signal power levels, the
determining of the average composite wideband power level, the
determining of the adaptive threshold, the detecting of the narrow band
interference, and the configuring of the filter are performed by a base
station.

10. The method of claim 9, wherein the base station is a cellular base
station.

11. The method of claim 1, comprising repeating the analyzing of the wide
frequency band, the detecting of the narrow band signal power levels, the
determining of the average composite wideband power level, the
determining of the adaptive threshold, the detecting of the narrow band
interference, and the configuring of the filter to suppress additional
narrow band interference.

12. The method of claim 1, wherein the determining of the average
composite wideband power level comprises not including a subset of the
narrow band signal power levels in the determination of the average
composite wideband power level.

13. The method of claim 12, wherein the subset of the narrow band signal
power levels have the largest signal strengths in the specified narrow
frequency bands.

14. A device, comprising: a radio frequency receiver; a filter; and a
circuit coupled to the radio frequency receiver and the filter, wherein
execution of instructions by the circuit cause the circuit to perform
operations comprising: causing the radio frequency receiver to scan a
wide frequency band; measuring power levels in narrow frequency bands
from signals provided by the radio frequency receiver; determining an
average wideband power level from at least a portion of the power levels
in the narrow frequency bands; determining a threshold from the average
wideband power level or the portion of the power levels in the narrow
frequency bands; detecting from the signals narrow band interference
based on the threshold; and configuring the filter to substantially
suppress the detected narrow band interference.

15. The device of claim 14, wherein the device is a base station.

16. The device of claim 15, wherein the base station comprises a cellular
base station.

17. The device of claim 14, wherein the filter has a variable stop band.

18. The device of claim 14, wherein the circuit further performs
operations comprising updating the threshold, the average wideband power
level, or both according to subsequent measurements of power levels in
the narrow frequency bands.

19. A memory device, comprising instructions, which when executed by a
circuit, cause the circuit to perform operations comprising: measuring
power levels in narrow frequency bands of signals provided by a radio
frequency receiver configured to scan radio frequency signals over a wide
frequency band; calculating an average wideband power level from at least
a portion of the measured power levels; determining a threshold from the
average wideband power level, the portion of the measured power levels in
the narrow frequency bands, or both; detecting from the signals narrow
band interference based on the threshold; and substantially suppressing
the detected narrow band interference.

20. The memory device of claim 19, wherein the threshold has a power
level that exceeds the average wideband power level.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent application Ser.
No. 11/971,017, filed Jan. 8, 2008, which is a divisional of U.S.
application Ser. No. 09/827,641, filed on Apr. 6, 2001, now U.S. Pat. No.
7,317,698, which is a continuation-in-part of U.S. patent application
Ser. No. 09/301,477, filed on Apr. 28, 1999, now U.S. Pat. No. 6,807,405,
which claims priority to Canadian Patent 2,260,653, filed Feb. 2, 1999.
U.S. application Ser. No. 09/827,641, filed Apr. 6, 2001, now U.S. Pat.
No. 7,317,698, also claims priority to U.S. Provisional Application
60/195,387, filed Apr. 7, 2000. All sections of U.S. patent application
Ser. No. 11/971,017 are incorporated herein by reference in their
entirety.

FIELD OF THE DISCLOSURE

[0002] The present invention is directed to communication systems and,
more particularly, to a technique for detecting, identifying, extracting
and eliminating narrowband interference in a wideband communication
system.

BACKGROUND OF THE DISCLOSURE

[0003] As shown in FIG. 1, an exemplary telecommunication system 10 may
include mobile units 12, 13, a number of base stations, two of which are
shown in FIG. 1 at reference numerals 14 and 16, and a switching station
18 to which each of the base stations 14, 16 may be interfaced. The base
stations 14, 16 and the switching station 18 may be collectively referred
to as network infrastructure.

[0004] During operation, the mobile units 12, 13 exchange voice data or
other information with one of the base stations 14, 16, each of which are
connected to a conventional land line telephone network. For example,
information, such as voice information, transferred from the mobile unit
12 to one of the base stations 14, 16 is coupled from the base station to
the telephone network to thereby connect the mobile unit 12 with a land
line telephone so that the land line telephone may receive the voice
information. Conversely, information, such as voice information may be
transferred from a land line telephone to one of the base stations 14,
16, which, in turn, transfers the information to the mobile unit 12.

[0005] The mobile units 12, 13 and the base stations 14, 16 may exchange
information in either analog or digital format. For the purposes of this
description, it is assumed that the mobile unit 12 is a narrowband analog
unit and that the mobile unit 13 is a wideband digital unit.
Additionally, it is assumed that the base station 14 is a narrowband
analog base station that communicates with the mobile unit 12 and that
the base station 16 is a wideband digital base station that communicates
with the mobile unit 13.

[0006] Analog format communication takes place using narrowband 30
kilohertz (KHz) channels. The advanced mobile phone systems (AMPS) is one
example of an analog communication system in which the mobile unit 12
communicates with the base station 14 using narrowband channels.
Alternatively, the mobile unit 13 communicates with the base stations 16
using a form of digital communications such as, for example,
code-division multiple access (CDMA) or time-division multiple access
(TDMA). Digital communication takes place using spread spectrum
techniques that broadcast signals having wide bandwidths, such as, for
example, 1.25 megahertz (MHz) bandwidths.

[0007] The switching station 18 is generally responsible for coordinating
the activities of the base stations 14, 16 to ensure that the mobile
units 12, 13 are constantly in communication with the base station 14, 16
or with some other base stations that are geographically dispersed. For
example, the switching station 18 may coordinate communication handoffs
of the mobile unit 12 between the base stations 14 and another analog
base station as the mobile unit 12 roams between geographical areas that
are covered by the two base stations.

[0008] One particular problem that may arise in the telecommunication
system 10 is when the mobile unit 12 or the base station 14, each of
which communicate using narrowband channels, interfere with the ability
of the base station 16 to receive and process wideband digital signals
from the digital mobile unit 13. In such a situation, the narrowband
signal transmitted from the mobile unit 12 or the base station 14 may
interfere with the ability of the base station 16 to properly receive
wideband communication signals.

SUMMARY OF THE INVENTION

[0009] According to one aspect, the present invention may be embodied in a
method of detecting and eliminating narrowband interference in a wideband
communication signal having a frequency bandwidth with narrowband
channels disposed therein. Such a method may include scanning at least
some of the narrowband channels to determine signal strengths in at least
some of the narrowband channels and determining a threshold based on the
signal strengths in at least some of the narrowband channels.
Additionally, the method may include identifying narrowband channels
having signal strengths exceeding the threshold and assigning filters to
at least some of the narrowband channels having signal strengths
exceeding the threshold. Furthermore, the method may include determining
if the assigned filters are operating properly and bypassing any of the
assigned filters that are not operating properly.

[0010] According to a second aspect, the present invention may be embodied
in a system adapted to detect and eliminate narrowband interference in a
wideband communication signal having a frequency bandwidth with
narrowband channels disposed therein. Such a system may include a scanner
adapted to scan at least some of the narrowband channels to determine
signal strengths in at least some of the narrowband channels, a notch
module adapted to receive the wideband communication signal and to
selectively remove narrowband interference from the wideband
communication signal to produce a filtered wideband communication signal
and a bypass switch adapted to bypass the notch module when the bypass
switch is enabled. Furthermore, the system may include a controller
coupled to the scanner and to the notch module, wherein the controller is
adapted to determine a threshold based on the signal strengths in at
least some of the narrowband channels. Furthermore, the controller may be
adapted to identify narrowband channels having signal strengths exceeding
the threshold, to control the notch module to filter the wideband
communication signal at a frequency corresponding to a narrowband channel
having a signal strength exceeding the threshold, to determine if the
notch module is operating properly and to enable the bypass switch when
the notch module is not operating properly.

[0011] According to a third aspect, the present invention may be embodied
in a method of detecting and eliminating narrowband interference in a
wideband communication signal having a frequency bandwidth with
narrowband channels disposed therein. Such a method may include scanning
at least some of the narrowband channels to determine signal strengths in
at least some of the narrowband channels, determining a threshold based
on the signal strengths in at least some of the narrowband channels and
identifying fading narrowband channels having signal strengths that do
not exceed the threshold and that were previously identified as exceeding
the threshold, based on how long the identified narrowband channels have
not exceeded the threshold. Additionally, the method may include
filtering the wideband communication signal at a frequency corresponding
to a fading narrowband channel.

[0012] According to a fourth aspect, the present invention may be embodied
in a system adapted to detect and eliminate narrowband interference in a
wideband communication signal having a frequency bandwidth with
narrowband channels disposed therein. Such a system may include a scanner
adapted to scan at least some of the narrowband channels to determine
signal strengths in at least some of the narrowband channels in an order
representative of a probability that the narrowband channels will have
interference and a notch module adapted to receive the wideband
communication signal and to selectively remove narrowband interference
from the wideband communication signal to produce a filtered wideband
communication signal. The system may also include a controller coupled to
the scanner and to the notch module, wherein the controller is adapted to
determining a threshold based on the signal strengths in at least some of
the narrowband channels. The controller may be further adapted to
identify fading narrowband channels having signal strengths that do not
exceed the threshold and that were previously identified as exceeding the
threshold, based on how long the identified narrowband channels have not
exceeded the threshold and to control the notch module to filter the
wideband communication signal at a frequency corresponding to a fading
narrowband channel.

[0013] These and other features of the present invention will be apparent
to those of ordinary skill in the art in view of the description of the
preferred embodiments, which is made with reference to the drawings, a
brief description of which is provided below.

[0015]FIG. 2 is an exemplary illustration of a base station of FIG. 1;

[0016]FIG. 3 is an exemplary illustration of a frequency spectrum of a
wideband signal in the absence of interference;

[0017]FIG. 4 is an exemplary illustration of a frequency spectrum of a
wideband signal in the presence of three narrowband interferers;

[0018]FIG. 5 is an exemplary illustration of a frequency spectrum of a
wideband signal having three narrowband interferers removed therefrom;

[0019]FIG. 6 is an exemplary illustration of one embodiment of an
adaptive notch filter (ANF) module of FIG. 2;

[0020]FIG. 7 is an exemplary illustration of a second embodiment of an
ANF module of FIG. 2;

[0021] FIG. 8 is an exemplary illustration of a notch module of FIG. 7;

[0022]FIG. 9 is an exemplary illustration of a second embodiment of a
notch filter block of FIG. 8;

[0023]FIG. 10 is an exemplary flow diagram of a main routine executed by
the microcontroller of FIG. 7;

[0024]FIG. 11 is an exemplary flow diagram of a setup default values
routine executed by the microcontroller of FIG. 7;

[0025]FIG. 12 is an exemplary flow diagram of a built in test equipment
(BITE) test routine executed by the microcontroller of FIG. 7;

[0026]FIG. 13 is an exemplary flow diagram of a signal processing and
interference identification routine executed by the microcontroller of
FIG. 7;

[0027]FIG. 14 is an exemplary flow diagram of an interference extraction
routine executed by the microcontroller of FIG. 7;

[0028] FIG. 15 is an exemplary flow diagram of a fail condition check
routine executed by the microcontroller of FIG. 7;

[0029] FIGS. 16A and 16B form an exemplary flow diagram of a main routine
executed by the operations, alarms and metrics (OA&M) processor of FIG.
7;

[0030]FIG. 17 is an exemplary flow diagram of a prepare response routine
executed by the OA&M processor of FIG. 7; and

[0031] FIG. 18 is an exemplary flow diagram of a data buffer interrupt
function executed by the OA&M processor of FIG. 7.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] As disclosed in detail hereinafter, a system and/or a method for
detecting, identifying, extracting and reporting interference may be used
in a communication system. In particular, such a system or method may be
employed in a wideband communication system to protect against, or to
report the presence of, narrowband interference, which has deleterious
effects on the performance of the wideband communication system.

[0033] As shown in FIG. 2, the signal reception path of the base station
16, which was described as receiving narrowband interference from the
mobile unit 12 in conjunction with FIG. 1, includes an antenna 20 that
provides signals to a low noise amplifier (LNA) 22. The output of the LNA
22 is coupled to a splitter 24 that splits the signal from the LNA into a
number of different paths, one of which may be coupled to an adaptive
notch filter (ANF) module 26 and another of which may be coupled to a
narrowband receiver 28. The output of the ANF module 26 is coupled to a
wideband receiver 30, which may, for example, be embodied in a CDMA
receiver or any other suitable wideband receiver. The narrowband receiver
28 may be embodied in a 15 KHz bandwidth receiver or in any other
suitable narrowband receiver. Although only one signal path is shown in
FIG. 2, it will be readily understood to those having ordinary skill in
the art that such a signal path is merely exemplary and that, in reality,
a base station may include two or more such signal paths that may be used
to process main and diversity signals received by the base station 16.

[0034] The outputs of the narrowband receiver 28 and the wideband receiver
30 are coupled to other systems within the base station 16. Such systems
may perform voice and/or data processing, call processing or any other
desired function. Additionally, the ANF module 26 is also communicatively
coupled, via the Internet, telephone lines or any other suitable media,
to a reporting and control facility that is remote from the base station
16. In some networks, the reporting and control facility may be
integrated with the switching station 18. The narrowband receiver 28 is
communicatively coupled to the switching station 18 and may respond to
commands that the switching station 18 issues.

[0035] Each of the components 20-30 of the base station 16 shown in FIG.
2, except for the ANF module 26, may be found in a conventional wideband
cellular base station, the details of which are well known to those
having ordinary skill in the art. It will also be appreciated by those
having ordinary skill in the art that FIG. 2 does not disclose every
system or subsystem of the base station 16 and, rather, focuses on the
systems and subsystems of the base station 16 that are relevant to the
description of the present invention. In particular, it will be readily
appreciated that, while not shown in FIG. 2, the base station 16 includes
a transmission system or subsystem.

[0036] During operation of the base station 16, the antenna 20 receives
wideband signals that are broadcast from the mobile unit 13 and couples
such signals to the LNA 22, which amplifies the received signals and
couples the amplified signals to the splitter 24. The splitter 24 splits
the amplified signal from the LNA 22 and essentially puts copies of the
amplified signal on each of its output lines. The ANF module 26 receives
the signal from the splitter 24 and, if necessary, filters the wideband
signal to remove any undesired narrowband interference and couples the
filtered wideband signal to the wideband receiver 30.

[0037]FIG. 3 illustrates a frequency spectrum 40 of a wideband signal
that may be received at the antenna 20, amplified and split by the LNA 22
and the splitter 24 and coupled to the ANF module 26. If the wideband
signal received at the antenna 20 has a frequency spectrum 40 as shown in
FIG. 3, the ANF module 26 will not filter the wideband signal and will
simply couple the wideband signal directly through the ANF module 26 to
the wideband receiver 30.

[0038] However, as noted previously, it is possible that the wideband
signal transmitted by the mobile unit 13 and received by the antenna 20
has a frequency spectrum 42 as shown in FIG. 4. Such a frequency spectrum
42 includes not only the wideband signal from the mobile unit 13 having a
frequency spectrum similar to the frequency spectrum 40 of FIG. 3, but
includes three narrowband interferers 44, 46, 48, as shown in FIG. 4, one
of which may be from the mobile unit 12. If a wideband signal having a
frequency spectrum 42 including narrowband interferers 44, 46, 48 is
received by the antenna 20 and amplified, split and presented to the ANF
module 26, the ANF module 26 will filter the frequency spectrum 42 to
produce a filtered frequency spectrum 50 as shown in FIG. 5.

[0039] The filtered frequency spectrum 50 has the narrowband interferers
44, 46, 48 removed, therefore leaving a frequency spectrum 50 that is
very similar to the frequency spectrum 40, which does not include any
interference. The filtered wideband signal is then coupled from the ANF
module 26 to the wideband receiver 30, so that the filtered wideband
signal spectrum 50 may be demodulated. Although some of the wideband
signal was removed during filtering by the ANF module 26, sufficient
wideband signal remains to enable the wideband receiver 30 to recover the
information that was broadcast by a mobile unit. Accordingly, in general
terms, the ANF module 26 selectively filters wideband signals to remove
narrowband interference therefrom. Further detail regarding the ANF
module 26 and its operation is provided below in conjunction with FIGS.
6-17.

[0040] In general, one embodiment of an ANF module 60, as shown in FIG. 6,
scans the frequency spectrum of the signal provided by the splitter 24
and looks for narrowband interference therein. Such scanning may be
implemented by scanning to various known narrowband channels that exist
within the bandwidth of the wideband signal. For example, the ANF module
60 may scan to various AMPS channels that lie within the bandwidth of the
wideband signal. Alternatively, all of the frequency spectrum encompassed
by the wideband signal may be scanned. Either way, when narrowband
interference is detected in the wideband signal, the ANF module 60 moves
the narrowband interference into the notch of a notch filter, thereby
filtering the wideband signal to remove the narrowband interference.

[0041] In particular, as shown in FIG. 6, the signal from the splitter 24
is coupled to a first mixer 62, which receives an additional input from a
voltage controlled oscillator (VCO) 64. The first mixer 62 mixes the
signal from the splitter 26 with the signal from the VCO 64, thereby
shifting the frequency spectrum of the signal from the splitter 24 and
putting a portion of the shifted frequency spectrum located at
intermediate frequency (IF) into a notch frequency of a notch filter 66.
Accordingly, the component of the frequency shifted signal that is at the
IF is removed by the notch filter 66 having a notch frequency set at the
IF.

[0042] The resulting filtered signal is coupled from the notch filter 66
to a second mixer 68, which is also driven by the VCO 64. The second
mixer 68 mixes the notch filter output with the signal from the VCO 64 to
shift the frequency spectrum of the filtered signal back to an original
position that the signal from the splitter 24 had. The output of the
second mixer 68 is coupled to a band pass filter 70, which removes any
undesired image frequencies created by the second mixer 68.

[0043] In the system of FIG. 6, the narrowband interference present in the
wideband signal is mixed to the IF, which is the notch frequency of the
notch filter 66, by the first mixer 62 and is, therefore, removed by the
notch filter 66. After the narrowband interference has been removed by
the notch filter 66, the second mixer 68 restores the signal to its
original frequency position, except that the narrowband interference has
been removed. Collectively, the first mixer 62, the VCO 64, the notch
filter 66, the second mixer 68 and the band pass filter may be referred
to as an "up, down filter" or a "down, up filter."

[0044] The signal from the splitter 24 is also coupled to a bypass switch
72 so that if no narrowband interference is detected in the wideband
signal from the splitter 24, the bypass switch 72 may be enabled to
bypass the notch filter 66 and the mixers 62, 68, thereby passing the
signal from the splitter 24 directly to the wideband receiver 30.
Alternatively, if narrowband interference is detected, the bypass switch
72 is opened and the signal from the splitter 24 is forced to go through
the notch filter 66.

[0045] To detect the presence of narrowband interference and to effectuate
frequency scanning, a number of components are provided. A discriminator
74 receives the output signal from the first mixer 62 and detects signal
strength at the IF using a received signal strength indicator (RSSI) that
is tuned to the IF. The RSSI output of the discriminator 74 is coupled to
a comparator 76, which also receives a threshold voltage on a line 78.
When the RSSI signal from the discriminator 74 exceeds the threshold
voltage on the line 78, the comparator 76 indicates that narrowband
interference is present at the IF, which is the notch frequency of the
notch filter 66. When narrowband interference is detected, the sweeping
action of the VCO 64 is stopped so that the notch filter 66 can remove
the interference at the IF.

[0046] To affect the sweeping action of the VCO 64, the output of the
comparator 76 is coupled to a sample and hold circuit 80, which receives
input from a voltage sweep generator 82. Generally, when no interference
is detected by the comparator 76, the output of the voltage sweep
generator 82 passes through the sample and hold circuit 80 and is applied
to a summer 84, which also receives input from a low pass filter 86 that
is coupled to the output of the discriminator 74. The summer 84 produces
a signal that drives the VCO 64 in a closed loop manner. As the voltage
sweep generator 82 sweeps its output voltage over time, the output of the
summer 84 also sweeps, which causes the frequency output of the VCO 64 to
sweep over time. The sweeping output of VCO 64, in conjunction with the
discriminator 74 and the comparator 76, scan the signal from the splitter
24 for interference. As long as the comparator 76 indicates that
narrowband interference is not present, the switch 72 is held closed,
because there is no need to filter the signal from the splitter 24.

[0047] However, when the comparator 76 detects narrowband interference in
the signal from the splitter 24 (i.e., when the RSSI exceeds the voltage
on the line 78), the sample and hold circuit 80 samples the output of the
voltage sweep generator 82 and holds the sampled voltage level, thereby
providing a fixed voltage to the summer 84, which, in turn, provides a
fixed output voltage to the VCO 64. Because a fixed voltage is provided
to the VCO 64, the frequency output by the VCO 64 does not change and the
signal from the splitter 24 is no longer scanned, but is frequency
shifted so that the narrowband interference is moved to the IF, which is
the notch frequency of the notch filter 66. Additionally, when the
comparator 76 indicates that narrowband interference is present, the
switch 72 opens and the only path for the signal from the splitter 24 to
take is the path through the mixers 62, 68 and the notch filter 66.

[0048] The threshold voltage on the line 78 may be hand tuned or may be
generated by filtering some received signal strength. Either way, the
voltage on the line 78 should be set so that the comparator 76 does not
indicate that interference is present when only a wideband signal, such
as the signal shown in FIG. 3, is present, but only indicates
interference when a signal having narrowband interference is present. For
example, the frequency spectrum 42 shown in FIG. 4, shows three
narrowband interferers 44, 46, 48, only one of the interferers would be
needed for the comparator 76 to indicate the presence of narrowband
interference. As will be readily appreciated, the embodiment shown in
FIG. 6 is only able to select and filter a single narrowband interferer
within a wideband signal.

[0049] As shown in FIG. 7, a second embodiment of an ANF module 100, which
may filter a number of narrowband interferers, generally includes a
scanner 102, an analog to digital converter (A/D) 104, a microcontroller
106, an operations, alarms and metrics (OA&M) processor 108 and notch
modules, two of which are shown in FIG. 7 at reference numerals 110 and
112. The microcontroller 106 and the OA&M processor 108 may be embodied
in a model PIC 16C77-20P microcontroller, which is manufactured by
Microchip Technology, Inc., and a model 80386 processor, which is
manufactured by Intel Corp., respectively. Although they are shown and
described herein as separate devices that execute separate software
instructions, those having ordinary skill in the art will readily
appreciate that the functionality of the microcontroller 106 and the OA&M
processor 108 may be merged into a single processing device.

[0050] Additionally, the second embodiment of the ANF module 100 may
include a built in test equipment (BITE) module 114 and a bypass switch
116, which may be embodied in a model AS239-12 gallium arsenide
single-pole, double-throw switch available from Hittite. The
microcontroller 106 and the OA&M processor 108 may be coupled to external
memories 118 and 120, respectively.

[0051] In general, the scanner 102, which includes a mixer 130, a
discriminator 132 and a programmable local oscillator 134, interacts with
the A/D 104 and the microcontroller 106 to detect the presence of
narrowband interference in the signal provided by the splitter 24. The
mixer 130 and the programmable local oscillator 134 may be embodied in a
model MD-54-0005 mixer available from M/A-Com and a model AD9831 direct
digital synthesizer, which is manufactured by Analog Devices, Inc.,
respectively. Additionally, the A/D 104 may be completely integrated
within the microcontroller 106 or may be a stand alone device coupled
thereto.

[0052] As described in further detail below, once narrowband interference
is detected in the signal from the splitter 24, the microcontroller 106,
via serial bus 136, controls the notch modules 110, 112 to remove the
detected narrowband interference. Although the second embodiment of the
ANF module 100, as shown in FIG. 7, includes two notch modules 110, 112,
additional notch modules may be provided in the ANF module 100. The
number of notch modules that may be used in the ANF module 100 is only
limited by the signal degradation that each notch module contributes.
Because multiple notch modules are provided, multiple narrowband
interferers may be removed from the wideband signal from the splitter 24.
For example, if three notch modules were provided, a wideband signal
having the frequency spectrum 42, as shown in FIG. 4, may be processes by
the ANF module 110 to produce a filtered wideband signal having the
frequency spectrum 50, as shown in FIG. 5.

[0053] The scanner 102 performs its function as follows. The signal from
the splitter 24 is coupled to the mixer 130, which receives an input from
the programmable local oscillator 134. The mixer 130 mixes the signals
from the splitter 24 down to an IF, which is the frequency that the
discriminator 132 analyses to produce an RSSI measurement that is coupled
to the A/D 104. The A/D 104 converts the RSSI signal from an analog
signal into a digital signal that may be processed by the microcontroller
106. The microcontroller 106 compares the output of the A/D 104 to an
adaptive threshold that the microcontroller 106 has previously determined
Details regarding how the microcontroller 106 determines the adaptive
threshold are provided hereinafter. If the microcontroller 106 determines
that the output from the A/D 104, which represents RSSI, exceeds the
adaptive threshold, one of the notch modules 110, 112 may be assigned to
filter the signal from the splitter 24 at the IF having an RSSI that
exceeds the adaptive threshold.

[0054] The microcontroller 106 also programs the programmable local
oscillator 134 so that the mixer 130 moves various portions of the
frequency spectrum of the signal from the splitter 24 to the IF that the
discriminator 132 processes. For example, if there are 59 narrowband
channels that lie within the frequency band of a particular wideband
channel, the microcontroller 106 will sequentially program the
programmable local oscillator 134 so that each of the 59 channels is
sequentially mixed down to the IF by the mixer 132 so that the
discriminator 132 can produce RSSI measurements for each channel.
Accordingly, the microcontroller 106 uses the programmable local
oscillator 134, the mixer 130 and the discriminator 132 to analyze the
signal strengths in each of the 60 narrowband channels lying within the
frequency band of the wideband signal. By analyzing each of the channels
that lie within the frequency band of the wideband signal, the
microcontroller 106 can determine an adaptive threshold and can determine
whether narrowband interference is present in one or more of the
narrowband channels.

[0055] Once channels having narrowband interference are identified, the
microcontroller 106 may program the notch modules 110, 112 to remove the
most damaging interferers, which may, for example, be the strongest
interferers. As described in detail hereinafter, the microcontroller 106
may also store lists of channels having interferers, as well as various
other parameters. Such a list may be transferred to the reporting and
control facility or a base station, via the OA&M processor 108, and may
be used for system diagnostic purposes.

[0056] Diagnostic purposes may include, but are not limited to,
controlling the narrowband receiver 28 to obtain particular information
relating to an interferer and retasking the interferer by communicating
with its base station. For example, the reporting and control facility
may use the narrowband receiver 28 to determine the identity of an
interferer, such as a mobile unit, by intercepting the electronic serial
number (ESN) of the mobile unit, which is sent when the mobile unit
transmits information on the narrowband channel. Knowing the identity of
the interferer, the reporting and control facility may contact
infrastructure that is communicating with the mobile unit and may request
the infrastructure to change the transmit frequency of the mobile unit
(i.e., the frequency of the narrowband channel on which the mobile unit
is transmitting) or may request the infrastructure to drop communications
with the interfering mobile unit all together.

[0057] Additionally, diagnostic purposes may include using the narrowband
receiver 28 to determine a telephone number that the mobile unit is
attempting to contact and, optionally handling the call. For example, the
reporting and control facility may use the narrowband receiver 28 to
determine that the user of the mobile unit was dialing 911, or any other
emergency number, and may, therefore, decide that the narrowband receiver
28 should be used to handle the emergency call by routing the output of
the narrowband receiver 28 to a telephone network.

[0058] FIG. 8 reveals further detail of one of the notch modules 110, it
being understood that any other notch modules used in the ANF module 100
may be substantially identical to the notch module 110. In general, the
notch module 110 is an up, down or down, up filter having operational
principles similar to the ANF module 60 described in conjunction with
FIG. 6. In particular, the notch module 110 includes first and second
mixers 150, 152, each of which receives an input signal from a phase
locked loop (PLL) 154 that is interfaced through a logic block 156 to the
serial bus 136 of the microcontroller 106. Disposed between the mixers
150, 152 is a notch filter block 158, further detail of which is
described below. In practice, the mixers 150, 152 may be embodied in
model MD54-0005 mixers that are available from M/A-Com and the PLL 154
may be embodied in a model LMX2316® frequency synthesizer that is
commercially available from National Semiconductor.

[0059] During operation of the ANF module 100, the microcontroller 106
controls the PLL 154 to produce an output signal that causes the first
mixer 150 to shift the frequency spectrum of the signal from the splitter
24 to an IF, which is the notch frequency of the notch filter block 158.
Alternatively, in the case of cascaded notch modules, the notch module
may receive its input from another notch module and not from the splitter
24. The output of the PLL 154 is also coupled to the second mixer to
shift the frequency spectrum of the signal from the notch filter block
158 back to its original position as it was received from the splitter 24
after the notch filter block 158 has removed narrowband interference
therefrom. The output of the second mixer 152 is further coupled to a
filter 160 to remove any undesired image frequencies that may be produced
by the second mixer 152. The output of the filter 160 may be coupled to
an additional notch module (e.g., the notch module 112) or, if no
additional notch modules are used, may be coupled directly to the
wideband receiver 30.

[0060] Additionally, the notch module 110 includes a bypass switch 164
that may be used to bypass the notch module 110 in cases where there is
no narrowband interference to be filtered or in the case of a notch
module 110 failure. For example, the microcontroller 106 closes the
bypass switch 164 when no interference is detected for which the notch
module 110 is used to filter. Conversely, the microcontroller 106 opens
the bypass switch 164 when interference is detected and the notch module
110 is to be used to filter such interference.

[0061] As shown in FIG. 8, the notch filter block 158 includes a filter
165, which may be, for example a filter having a reject band that is
approximately 15 KHz wide at -40 dB. The reject band of the filter 165
may be fixed at, for example, a center frequency of 150 MHz or at any
other suitable frequency at which the IF of the mixer 150 is located.

[0062] Although the notch filter block 158 of FIG. 8 shows only a single
filter 165, as shown in FIG. 9, a second embodiment of a notch filter
block 166 may include a switch 170 and multiple filters 172-178. In such
an arrangement, each of the filters 172-178 has a notch frequency tuned
to the IF produced by the first mixer 150. Additionally, each of the
filters 172-178 may have a different reject bandwidth at -40 dB. For
example, as shown in FIG. 9, the filters 172-178 have reject bandwidths
of 15 KHz to 120 KHz. The use of filters having various reject bandwidths
enables the ANF module 100 to select a filter having an optimal reject
bandwidth to best filter an interferer.

[0063] During operation, of the second embodiment of the notch filter
block 166, the microcontroller 106 controls the switch 170 to route the
output signal from the first mixer 150 to one of the filters 172-178. The
microcontroller 106, via the switch 170, selects the filter 172-178
having a notch switch best suited to filter interference detected by the
microcontroller 106. For example, if the microcontroller 106 determines
that there is interference on a number of contiguous channels, the
microcontroller 106 may use a filter 172-178 having a notch width wide
enough to filter all such interference, as opposed to using a single
filters to filter interference on each individual channel. Additionally,
a single filter having a wide bandwidth may be used when two narrowband
channels having interference are separated by a narrowband channel that
does not have narrowband interference. Although the use of a single wide
bandwidth filter will filter a narrowband channel not having interference
thereon, the wideband signal information that is lost is negligible.

[0064] Having described the detail of the hardware aspects of the system,
attention is now turned to the software aspects of the system. Of course,
it will be readily understood by those having ordinary skill in the art
that software functions may be readily fashioned into hardware devices
such as, for example, application specific integrated circuits (ASICs).
Accordingly, while the following description pertains to software, such a
description is merely exemplary and should not be considered limiting in
any way.

[0065] That being said, FIGS. 10-15 include a number of blocks
representative of software or hardware functions or routines. If such
blocks represent software functions, instructions embodying the functions
may be written as routines in a high level language such as, for example,
C, or any other suitable high level language, and may be compiled into a
machine readable format. Alternatively, instructions representative of
the blocks may be written in assembly code or in any other suitable
language. Such instructions may be stored within the microcontroller 106
or may be stored within the external memory 118 and may be recalled
therefrom for execution by the microcontroller 106.

[0066] A main routine 200, as shown in FIG. 10, includes a number of
blocks or routines that are described at a high level in connection with
FIG. 10 and are described in detail with respect to FIGS. 11-15. The main
routine 200 begins execution at a block 202 at which the microcontroller
102 sets up default values and prepares to carry out the functionality of
the ANF module 100. After the setup default values function is complete,
control passes to a block 204, which performs a built-in test equipment
(BITE) test of the ANF module 100.

[0067] After the BITE test has been completed, control passes from the
block 204 to a block 206, which performs signal processing and
interference identification. After the interference has been identified
at the block 206, control passes to a block 208 where the identified
interference is extracted from the wideband signal received by the ANF
module 100.

[0068] After the interference has been extracted at the block 208, control
passes to a block 210 at which a fail condition check is carried out. The
fail condition check is used to ensure that the ANF module 100 is
operating in a proper manner by checking for gross failures of the ANF
module 100.

[0069] After the fail condition check completes, control passes from the
block 210 to a block 212, which performs interference data preparation
that consists of passing information produced by some of the blocks
202-210 from the microcontroller 106 to the OA&M 108. Upon completion of
the interference data preparation, the main routine 200 ends its
execution. The main routine 200 may be executed by the microcontroller
106 at time intervals such as, for example, every 20 MS.

[0070] As shown in FIG. 11, the setup default values routine 202 begins
execution at a block 220 at which the microcontroller 106 tunes the
programmable local oscillator 134 to scan for interference on a first
channel designated as F1. For example, as shown in FIG. 11, F1 may be
836.52 megahertz (MHz). Alternatively, as will be readily appreciated by
those having ordinary skill in the art, the first channel to which the
ANF module 100 is tuned may be any suitable frequency that lies within
the frequency band or guard band of a wideband channel.

[0071] After the microcontroller 106 is set up to scan for interference on
a first frequency, control passes from the block 220 to a block 222,
which sets up default signal to noise thresholds that are used to
determine the presence of narrowband interference in wideband signals
received from the splitter 24 of FIG. 2. Although subsequent description
will provide detail on how adaptive thresholds are generated, the block
222 merely sets up an initial threshold for determining presence of
narrowband interference.

[0072] After the default thresholds have been set at the block 222 control
passes to a block 224 at which the microcontroller 106 reads various
inputs, establishes serial communication with the notch modules 110, 112
and any other serial communication devices, as well as establishes
communications with the OA&M processor 108. After the block 224 completes
execution, the setup default values routine 202 returns control to the
main program and the block 204 is executed.

[0073]FIG. 12 reveals further detail of the BITE test routine 204, which
begins execution after the routine 202 completes. In particular, the BITE
test routine 204 begins execution at a block 240, at which the
microcontroller 106 puts the notch modules 110, 112 in a bypass mode by
closing their bypass switches 190. After the notch modules 110, 112 have
been bypassed, the microcontroller 106 programs the BITE module 114 to
generate interferers that will be used to test the effectiveness of the
notch modules 110, 112 for diagnostic purposes. After the notch modules
110, 112 have been bypassed and the BITE module 114 is enabled, control
passes from the block 240 to a block 242.

[0074] At the block 242, the microcontroller 106 reads interferer signal
levels at the output of the notch module 112 via the A/D 104. Because the
notch modules 110, 112 have been bypassed by the block 240, the signal
levels at the output of the notch module 112 should include the
interference that is produced by the BITE module 114.

[0075] After the interferer signal levels have been read at the block 242,
a block 244 determines whether the read interferer levels are
appropriate. Because the notch modules 110, 112 have been placed in
bypass mode by the block 240, the microcontroller 106 expects to see
interferers at the output of the notch module 112. If the levels of the
interferer detected at the output of the notch module 112 are not
acceptable (i.e., are too high or too low), control passes from the block
244 to a block 246 where a system error is declared. Declaration of a
system error may include the microcontroller 106 informing the OA&M
processor 108 of the system error. The OA&M processor 108, in turn, may
report the system error to a reporting and control facility.
Additionally, declaration of a system error may include writing the fact
that a system error occurred into the external memory 118 of the
microcontroller 106.

[0076] Alternatively, if the block 244 determines that the interferer
levels are appropriate, control passes from the block 244 to a block 248
at which the microcontroller 106 applies one or more of the notch
modules, 110, 112. After the notch modules 110, 112 have been applied
(i.e., not bypassed) by the block 248, control passes to a block 250,
which reads the signal level at the output of the notch module 112.
Because the BITE module 114 produces interference at frequencies to which
the notch filters are applied by the block 248, it is expected that the
notch modules 110, 112 remove such interference.

[0077] After the signal levels are read by the block 250, control passes
to a block 252, which determines if interference is present. If
interference is present, control passes from the block 252 to the block
246 and a system error is declared because one or more of the notch
modules 110, 112 are not functioning properly because the notch modules
110, 112 should be suppressing the interference generated by the BITE
module 114. Alternatively, if no interference is detected at the block
252, the ANF module 100 is functioning properly and is, therefore, set to
a normal mode of operation at a block 254. After the block 254 or the
block 246 have been executed, the BITE test routine 204 returns control
to the main program 200, which begins executing the block 206.

[0078] As shown in FIG. 13, the signal processing and interference
identification routine 206 begins execution at a block 270. At the block
270, the microprocessor 106 controls the programmable local oscillator
134 so that the microcontroller 106 can read signal strength values for
each of the desired channels via the discriminator 132 and the A/D 104.
In particular, the microcontroller 106 may control the programmable local
oscillator 134 to tune sequentially to a number of known channels. The
tuning moves each of the known channels to the IF so that the
discriminator 132 can make an RSSI reading of the signal strength of each
channel. Optionally, if certain channels have a higher probability of
having interference than other channels, the channels having the higher
probability may be scanned first. Channels may be determined to have a
higher probability of having interference based on historical
interference patters or interference data observed by the ANF module 100.

[0079] Additionally, at the block 270, the microcontroller 106 controls
the programmable local oscillator 134 to frequency shift portions of the
guard bands to the IF so that the discriminator 132 can produce RSSI
measurements of the guard bands. Because the guard bands are outside of a
frequency response of a filter disposed within the wideband receiver 30,
the block 270 compensates guard band signal strength reading by reducing
the values of such readings by the amount that the guard bands will be
attenuated by a receiver filter within the wideband receiver 30.
Compensation is carried out because the ANF module 100 is concerned with
the deleterious effect of narrowband signals on the wideband receiver 30.
Accordingly, signals having frequencies that lie within the passband of
the filter of the wideband receiver 30 do not need to be compensated and
signals falling within the guard band that will be filtered by the
receive filter of the wideband receiver 30 need to be compensated.
Essentially, the guard band compensation has a frequency response that is
the same as the frequency response of the wideband receiver filter. For
example, if a wideband receiver filter would attenuate a particular
frequency by 10 dB, the readings of guard bands at that particular
frequency would be attenuated by 10 dB.

[0080] After the block 270 is completed, control passes to a block 272,
which selects a number of channels having the highest signal levels.
Commonly, the number of channels that will be selected by the block 272
corresponds directly to the number of notch modules, 110, 112 that are
employed by a particular ANF module 100. After the channels having the
highest signal levels are selected by the block 272, control passes from
the block 272 to a block 274.

[0081] At the block 274, the microcontroller 106 determines an adaptive
threshold by calculating an average signal strength value for the desired
channels read by the block 270. However, the average is calculated
without considering the channels having the highest signal levels that
were selected by the block 272. Alternatively, it would be possible to
calculate the average by including the signal levels selected by the
block 272. The block 274 calculates an average that will be compensated
by an offset and used to determine whether narrowband interference is
present on any of the desired channels read by the block 270.

[0082] After the block 274 completes execution control passes to a block
276, which compares the signal strength values of the channels selected
by the block 272 to the adaptive threshold, which is the sum of the
average calculated by the block 274 threshold and an offset. If the
selected channels from the block 272 have signal strengths that exceeds
the adaptive threshold, control passes to a block 278.

[0083] The block 278 indicates the channels on which interference is
present based on the channels that exceeded the adaptive threshold. Such
an indication may be made by, for example, writing information from the
microcontroller 106 to the external memory 118, which is passed to the
OA&M processor 108. After the interferers have been indicated by the
block 278, control passes to a block 280. Additionally, if none of the
channels selected by the block 272 have signal strengths that exceed the
adaptive threshold, control passes from the block 276 to the block 280.

[0084] At the block 280, the microcontroller 106 updates an interference
data to indicate on which channels interferers were present. In
particular, each frame (e.g., 20 ms) the microcontroller 106 detects
interferers by comparing power levels (RSSI) on a number of channels to
the threshold level. When an inteferer is detected, data for that
interferer is collected for the entire time that the interferer is
classified as an interferer (i.e., until the RSSI level of the channel
falls below the threshold for a sufficient period of time to pass the
hang time test that is described below). All of this information is
written to a memory (e.g., the memory 118 or 120), to which the OA&M
processor 108 has access. As described below, the OA&M processor 108
processes this information to produce the interference report.

[0085] Additionally, the block 280 reads input commands that may be
received from the OA&M processor 108. Generally, such commands may be
used to perform ANF module 100 configuration and measurement. In
particular, the commands may be commands that put the ANF module 100 in
various modes such as, for example, a normal mode, a test mode in which
built in test equipment is employed or activated, or a bypass mode in
which the ANF module 100 is completely bypassed. Additionally, commands
may be used to change identifying characteristics of the ANF module 100.
For example, commands may be used to change an identification number of
the ANF module 100, to identify the type of equipment used in the ANF
module 100, to identify the geographical location of the ANF module 100
or to set the time and date of a local clock within the ANF module 100.
Further, commands may be used to control the operation of the ANF module
100 by, for example, adding, changing or deleting the narrowband channels
over which the ANF module 100 is used to scan or to change manually the
threshold at which a signal will be classified as an interferer. Further,
the attack time and the hang time, each of which is described below, may
be changed using commands. Additionally, a command may be provided to
disable the ANF module 100.

[0086] After the block 280 has completed execution, the signal processing
and interference identification routine 260 returns control back to the
main routine 200, which continues execution at the block 208.

[0087] As shown in FIG. 14, the interference extraction routine 208 begins
execution at a block 290, which compares the time duration that an
interferer has been present with a reference time called "duration time
allowed," which may also be referred to as "attack time." If the
interferer has been present longer than the attack time, control passes
to a block 292. Alternatively, if the interferer has not been present
longer than the duration time allowed, control passes to a block 296,
which is described in further detail below. Essentially, the block 290
acts as a hysteresis function that prevents filters from being assigned
to temporary interferers immediately as such interferers appear.
Typically, the duration time allowed may be on the order of 20
milliseconds (ms), which is approximately the frame rate of a CDMA
communication system. As will be readily appreciated by those having
ordinary skill in the art, the frame rate is the rate at which a base
station and a mobile unit exchange data. For example, if the frame rate
is 20 ms, the mobile unit will receive a data burst from the base station
every 20 ms. The block 90 accommodates mobile units that are in the
process of initially powering up. As will be appreciated by those having
ordinary skill in the art, mobile units initially power up with a
transmit power that is near the mobile unit transmit power limit. After
the mobile unit that has initially powered up establishes communication
with a base station, the base station may instruct the mobile unit to
reduce its transmit power. As the mobile unit reduces its transmit power,
the mobile unit may cease to be an interference source to a base station
having an ANF module. Accordingly, the block 290 prevents the ANF module
100 from assigning a notch module 110, 112 to an interferer that will
disappear on its own within a short period of time.

[0088] At the block 292, the microcontroller 106 determines whether there
are any notch modules 110, 112 that are presently not used to filter an
interferer. If there is a notch module available, control passes from the
block 292 to a block 294, which activates an available notch module and
tunes that notch module to filter the interferer that is present in the
wideband signal from the splitter 24. After the block 294 has completed
execution, control passes to the block 296, which is described below.

[0089] If, however, the block 292 determines that there are no notch
modules available, control passes from the block 292 to a block 298,
which determines whether the present interferer is stronger than any
interferer to which a notch module is presently assigned. Essentially,
the block 298 prioritizes notch modules so that interferers having the
strongest signal levels are filtered first. If the block 298 determines
that the present interferer is not stronger than any other interferer to
which a notch module is assigned, control passes from the block 298 to
the block 296.

[0090] Alternatively, if the present interferer is stronger than an
interferer to which a notch module is assigned, control passes from the
block 298 to a block 300. The block 300 determines whether the interferer
that is weaker than the present interferer passes a hang time test. The
hang time test is used to prevent the ANF module 100 from deassigning a
notch module 110, 112 from an interferer when the interferer is in a
temporary fading situation. For example, if a mobile unit is generating
interference and a notch module 110, 112 has been assigned to filter that
interference, when the mobile unit enters a fading situation in which the
interference level is detected at an ANF module 100 becomes low, the ANF
module 100 does not deassign the notch module being used to filter the
fading interference until the interference has not been present for a
time referred to as hang time. Essentially, hang time is a hysteresis
function that prevents notch modules from being rapidly deassigned from
interferers that are merely temporarily fading and that will return after
time has passed. Hang time may be on the order of milliseconds of
seconds. Accordingly, if the interferer that is weaker than the present
interferer passes hang time, control passes to a block 302.
Alternatively, if the interferer weaker than the present interferer does
not pass hang time, the block 300 passes controlled to the block 296.

[0091] At the block 302, the microcontroller 106 deactivates the notch
module being used to filter the weaker interferer and reassigns that same
notch module to the stronger interferer. After the block 302 has
completed the reassignment of the notch module, control passes to the
block 296.

[0092] At the block 296, the microcontroller 106 rearranges interferers
from lowest level to highest level and assigns notches to the highest
level interferers. As with the block 298, the block 296 performs
prioritizing functions to ensure that the strongest interferers are
filtered with notch modules. Additionally, the block 296 may analyze the
interference pattern detected by the ANF module 100 and may assign
filters 172-178 having various notch widths to filter interferers. For
example, if the ANF module 100 detects interference on contiguous
channels collectively have a bandwidth of 50 KHz, the 50 KHz filter 176
of the notch filter block 158 may be used to filter such interference,
rather than using four 15 KHz filters. Such a technique essentially frees
up notch filter modules 110, 112 to filter additional interferers.

[0093] After the block 296 has completed execution, control passes to a
block 304, which updates interference data by sending a list of channels
and their interference status to a memory (e.g., the memory 118 or 120)
that may be accessed by the OA&M processor 108. After the block 304 has
completed execution, the interference extraction routine 208 returns
control to the main module 200, which continues execution at the block
210.

[0094] At the block 210, as shown in FIG. 15, the microcontroller 106
determines if a gross failure has occurred in the ANF module 100. Such a
determination may be made by, for example, determining if a voltage
output from a voltage regulator of the ANF module 100 has an appropriate
output voltage. Alternatively, gross failures could be determined by
testing to see if each of the notch modules 110, 112 are inoperable. If
each of the notch modules is inoperable, it is likely that a gross
failure of the ANF module 100 has occurred. Either way, if a gross
failure has occurred, control passes from the block 320 to a block 322 at
which point the microcontroller 106 enables the bypass switch 116 of FIG.
7 to bypass all of the notch modules 110, 112 of the ANF module 100,
thereby effectively connecting the splitter 24 directly to the wideband
receiver 30. After the execution of the block 322, or if the block 320
determines that a gross failure has not occurred, control passes back to
the main routine 200, which continues execution at the block 212. At the
block 212, the interference data that was written to the memory 118 or
120, is passed to the OA&M processor 108.

[0095] Having described the functionality of the software that may be
executed by the microcontroller 106, attention is now turned to the OA&M
processor 108 of FIG. 7. If the blocks shown in FIG. 16 represent
software functions, instructions embodying the functions may be written
as routines in a high level language such as, for example, C, or any
other suitable high level language, and may be compiled into a machine
readable format. Alternatively, instructions representative of the blocks
may be written in assembly code or in any other suitable language. Such
instructions may be stored within the OA&M processor 108 or may be stored
within the external memory 120 and may be recalled therefrom for
execution by the OA&M controller 108.

[0096] In particular, as shown in FIGS. 16A and 16B, which are referred to
herein collectively as FIG. 16, a main routine 340 executed by the OA&M
processor 108 may begin execution at a block 342, at which the OA&M
processor 108 is initializes itself by establishing communication,
checking alarm status and performing general housekeeping tasks. At the
block 342, the OA&M processor 108 is initialized and passes control to a
block 344.

[0097] At the block 344, the OA&M processor 108 determines whether there
is new data to read from an OA&M buffer (not shown). If the block 344
determines that there is new data to read, control passes to a block 346,
which determines if the new data is valid. If the new data is valid,
control passes from the block 346 to a block 348, which read the data
from the OA&M buffer. Alternatively, if the block 346 determines that the
new data is not valid, control passes from the block 346 to a block 350,
which resets the OA&M buffer. After the execution of either the block 348
or the block 350, control passes to a block 352, which is described in
further detail hereinafter.

[0098] Returning to the block 344, if the block 344 determines that there
is no new data to be read, control passes to a block 360, which
calculates power levels of each of the channels scanned by the ANF module
100. The OA&M processor 108 is able to calculate power levels at the
block 360 because the data generated as the microcontroller 106 of the
ANF module 100 scans the various channels is stored in a buffer that may
be read by the OA&M processor 108.

[0099] After the power levels have been calculated at the block 360,
control passes to a block 362, which determines if the any of the
calculated power levels exceed a predetermined threshold. If the
calculated power levels do exceed the predetermined threshold, control
passes from the block 362 to a block 364, which tracks the duration and
time of the interferer before passing control to a block 366.
Alternatively, if the block 362 determines that none of the power levels
calculated to the block 360 exceed the predetermined threshold, control
passes from the block 362 directly to the block 366.

[0100] The block 366 determines whether the interferer being evaluated was
previously denoted as an interferer. If the block 366 determines that the
interferer being evaluated was not previously an interferer, control
passes to the block 352. Alternatively, the block 366 passes control to a
block 368.

[0101] At the block 368, the OA&M processor 108 determines whether the
present interferer was a previous interferer that has disappeared, if so,
the OA&M processor 108 passes control to a block 370. Alternatively, if
the present interferer has not disappeared, control passes from the block
368 to a block 372.

[0102] At the block 370, the OA&M processor 108 stores the interferer
start time and duration. Such information may be stored within the OA&M
processor 108 itself or may be stored within the external memory 120 of
the OA&M processor 108. After the block 370 has completed execution,
control passes to the block 352. At the block 372, the duration of the
interferer is incremented to represent the time that the interferer has
been present. After the execution of block 372, control passes to the
block 352.

[0103] The block 352 determines whether a command has been received at the
OA&M processor 108 from the reporting and control facility. If such a
command has been received, control passes from the block 352 to a block
380. At the block 380, the OA&M processor 108 determines if the command
is for the microcontroller 106 of the ANF module 100, or if the command
is for the OA&M processor 108. If the command is for the microcontroller
106, control passes from the block 380 to a block 382, which sends the
command to the microcontroller 106. After the execution of the block 382,
the main routine 340 ends.

[0104] Alternatively, if the command received by the OA&M processor 108 is
not a command for the microcontroller 106, control passes from the block
380 to a block 384, which prepares a response to the command. Responses
may include simple acknowledgments or may include responses including
substantive data that was requested. Further detail on the block 384 is
provided in conjunction with FIG. 17. After the block 384 has prepared a
response, a block 386 activates the serial interrupt of the OA&M
processor 108 and ends execution of the main routine 340.

[0105] Alternatively, if the block 352 determines that a command was not
received, control passes from the block 352 to a block 390, which
determines if the bypass switch 116 of FIG. 7 is closed (i.e., the bypass
is on). If the block 390 determines that the bypass is not on, the
execution of the main routine 340 ends. Alternatively, if the block 390
determines that the bypass is on, control passes from the block 390 to a
block 392.

[0106] At the block 392, the OA&M processor 108 determines whether there
was a prior user command to bypass the ANF module 100 using the bypass
switch 116. If such a user command was made, execution of the main
routine 340 ends. Alternatively, if there was no prior user command
bypass the ANF module 100, control passes from the block 392 to a block
394, which compares the bypass time to a hold time. If the bypass time
exceeds the hold time, which may be, for example, one minute, control
passes from the block 394 to a block 396.

[0107] At the block 396, an alarm is generated by the OA&M processor 108
and such an alarm is communicated to a reporting and control facility by,
for example, pulling a communication line connected to the reporting and
control facility to a 24 volt high state. After the execution of the
block 396, the main routine 340 ends.

[0108] Alternatively, if the block 394 determines that the bypass time has
not exceeded the hold time, control passes from the block 394 to a block
398, which counts down the hold time, thereby bringing the bypass time
closer to the hold time. Eventually, after the block 398 sufficiently
decrements the hold time, the block 394 will determine that the bypass
time does exceed the hold time and pass control to the block 396. After
the block 398 has completed execution, the main routine 340 ends.

[0109] As shown in FIG. 17, the prepare response routine 384 begins
execution at a block 400. At the block 400, the OA&M processor 108 reads
information that the microcontroller 106 has written into a buffer (e.g.,
the memory 118 or 120) and calculates the duration of the interferers
that are present, calculates interferer power levels and calculates the
average signal power. This information may be stored locally within the
ANF module 100 or may be reported back to a network administrator in real
time. Such reporting may be performed wirelessly, over dedicated lines or
via an Internet connection. The interferer power levels and the average
signal power may be used to evaluate the spectral integrity of a
geographic area to detect the presence of any fixed interferers that may
affect base station performance. Additionally, such information may be
used to correlate base station performance with the interference
experienced by the base station. After the block 400 completes execution,
control passes through a block 402.

[0110] At the block 402, the OA&M processor 108 adds real time markers to
the information calculated in the block 400 and stores the report
information including the real time markers and the information
calculated in the block 400. Such information may be stored within the
OA&M processor 108 itself or may be stored within the external memory 120
of the OA&M processor 108.

[0111] After the block 402 has completed execution, control passes to a
block 404, which determines whether a command has been received by the
ANF module 100. Such commands would be received from a reporting and
control facility. If the block 404 determines that no command has been
received by the OA&M processor 108, control passes from the block 404
back to the main routine 340, which continues execution at the block 386.

[0112] Alternatively, if the block 404 determines that a command has been
received by the OA&M processor 108, control passes from the block 404 to
a block 406, which determines if the received command is a control
command that would be used to control the operation of the ANF module 100
from a remote location, such as the reporting and control facility. If
the block 406 determines that the command received is a control command,
the block 406 transfers control to a block 408 which takes the action
prescribed by the command. Commands may include commands that, for
example, commands that enable or disable remote control of the ANF module
100, or may include any other suitable commands. After the execution of
the block 408, control passes from the prepare response routine 384 back
to the main routine 340, which then ends execution.

[0113] Alternatively, if the block 406 determines that the command
received by the OA&M processor 108 is not a control command, control
passes from the block 406 to a block 410, which determines if the
received command is a report command. If the command was not a report
command, the block 410 passes control back to the main routine 340.
Alternatively, if the block 410 determines that the received command is a
report command, control passes from the block 410 to a block 412, which
prepares and sends out the interference report. The interference report
may include information that shows the parameters of the most recent 200
interferers that were detected by the ANF module 100 and the information
on which the microcontroller 106 wrote to a memory 118, 120 that the OA&M
processor 108 accesses to prepare the interference report. The
interference report may include the frequency number (channel) on which
interference was detected, the RF level of the interferer, the time the
interferer appeared, the duration of the interferer and the wideband
signal power that was present when the interferer was present.

[0114] In addition to the interference report, the OA&M processor 108 may
prepare a number of different reports in addition to the interference
report. Such additional reports may include: mode reports (report the
operational mode of the ANF module 100), status reports (reports alarm
and system faults of the ANF module 100), software and firmware version
reports, header reports (reports base station name, wideband carrier
center frequency, antenna number and base station sector), date reports,
time reports, activity reports (reports frequency number, RF level,
interferer start time, interferer duration, and wideband channel power)
and summary reports.

[0115] The interference report may be used for network system diagnostic
purposes including determining when the network administrator should use
a narrowband receiver 28 to determine a telephone number that the mobile
unit is attempting to contact and, optionally handling the call. For
example, the reporting and control facility may use the narrowband
receiver 28 to determine that the user of the mobile unit was dialing
911, or any other emergency number, and may, therefore, decide that the
narrowband receiver 28 should be used to handle the emergency call by
routing the output of the narrowband receiver 28 to a telephone network.

[0116] Additionally, the interference report may be used to determine when
a network administrator should control the narrowband receiver 28 to
obtain particular information relating to an interferer and retasking the
interferer by communicating with its base station. For example, the
reporting and control facility may use the narrowband receiver 28 to
determine the identity of an interferer, such as a mobile unit, by
intercepting the electronic serial number (ESN) of the mobile unit, which
is sent when the mobile unit transmits information on the narrowband
channel. Knowing the identity of the interferer, the reporting and
control facility may contact infrastructure that is communicating with
the mobile unit and may request the infrastructure to change the transmit
frequency of the mobile unit (i.e., the frequency of the narrowband
channel on which the mobile unit is transmitting) or may request the
infrastructure to drop communications with the interfering mobile unit
all together.

[0117] Further, the interference reports may be used by a network
administrator to correlate system performance with the information
provided in the interference report. Such correlations could be used to
determine the effectiveness of the ANF module 100 on increasing system
capacity.

[0118] After the block 412 has completed execution, control passes back to
the main routine 340, which continues execution at the block 386.

[0119] Referring now to FIG. 18, a data buffer interrupt function 500 is
executed by the OA&M processor 108 and is used to check for, and indicate
the presence of, valid data. The function 500 begins execution at a block
502, which checks for data.

[0120] After the execution of the block 502, control passes to a block
504, which checks to see if the data is valid. If the block 504
determines that the data is valid, control passes from the block 504 to a
block 506, which sets a valid data indicator before the function 500
ends. Alternatively, if the block 504 determines that the data is not
valid, control passes from the block 504 to a block 508, which sets a not
valid data indicator before the function 500 ends.

[0121] Numerous modifications and alternative embodiments of the invention
will be apparent to those skilled in the art in view of the foregoing
description. For example, while the foregoing description specifically
addressed the concept of eliminating interference from signals on 30 KHz
narrowband channels interfering with a 1.25 MHz wideband signal, it will
be readily appreciated that such concepts could be applied to wideband
channels having, for example, 5, 10 or 15 MHz bandwidths or to contiguous
channels that have an aggregate bandwidth of, for example, 5, 10 or 15
MHz. To accommodate such wider bandwidths, banks of downconverters may be
operated in parallel to cover 1.25 MHz block of the channel. Accordingly,
this description is to be construed as illustrative only and not as
limiting to the scope of the invention. The details of the structure may
be varied substantially without departing from the spirit of the
invention, and the exclusive use of all modifications, which are within
the scope of the appended claims, is reserved.